(1) Field of the Invention
The present invention relates generally to package sorting conveyors and, more particularly, to a system for adjusting and monitoring the distance between adjacent carts.
(2) Description of the Related Art
Conveyor systems having a number of individual carrying carts have been commonly used for many years to carry and sort packages or other items, such as mail. For example, U.S. Pat. No. 5,054,601 to Sjogren et al. discloses a package sorting conveyor comprised of a train of tilt tray carriers coupled in tandem to form a continuous loop. Each carrier includes a pivotally mounted tilt tray normally maintained in an upright position. The carriers are moved around the loop by a series of motors spaced around the loop. Branching out from the loop are outfeed chutes or the like for receiving packages from the carriers. When a particular carrier holding a particular package to be sorted reaches a selected outfeed chute, an actuator tilts the tray to dump the package into the outfeed chute. Another example of a typical package sorting conveyor is disclosed in International PCT Application Number PCT/DK90/00047 of Kosan Crisplant A/S, now U.S. Pat. No. 5,664,660.
Tilt tray sorters are installed as a closed-loop system. The track upon which the tilt trays are carried is manufactured to a fixed predetermined length based on the customer""s specific requirements and building layout. Tilt trays are built upon a carrier or chassis assembly that is also of fixed length (typically twenty or twenty-four inches). Therefore, a particular track length is designed to have a certain number of tilt tray carriers. For example, if a particular application requires a track length of 525 feet, and the application requires a tilt tray on a twenty-four inch chassis, the track will be engineered to be either 524 feet or 526 feet, and will hold either 262 or 263 tilt tray sorters, respectively.
A difficulty has arisen in the installation of tilt tray sorter conveyors, and installing them on the prospective site. Typically, because of site variables and manufacturing tolerances, the installation of the carriers upon the track does not match in the field. During installation, it is not uncommon for the track to be short or long by several inches.
The solution in the past was to build a xe2x80x9cTAKE-UPxe2x80x9d using two expansion joints, which would allow the track installers to move large sections of track, after installation, to correct for the variables. The take-up was a movable platform, typically under a curved section of track. The track was fitted with expansion joints as necessary at each end of the curve. If the track needed to be lengthened, the curve was physically picked up and moved to extend the track, and expansion joints were placed on the track where it was lengthened. If the track needed to be shortened, portions of the track could be machined and the curve physically picked up and moved to shorten the track. The location of the expansion joint or machining caused a problem because of the noise that would be generated as the carts would move over this section of track. All of this was time consuming and required skilled experienced labor.
Rather than lengthening or shortening the track, a second way to accommodate for this installation variable was to lengthen the train of carts. This was done by installing spacers in the linkage of the carriers. The typical carrier has a form of ball joint connection between the carriers. In certain systems, the trailing carrier had a ball assembly, on an extending rod bolted to the axis frame. Adding spacers between the extending rod and the frame could effectively lengthen the extending rod. For example, if the track were two inches longer than anticipated, the installation team would install thirty-two {fraction (1/16)}th inch spacers on carts throughout the train. Arranging the spacers uniformly throughout the train of carriers was found to be preferable. The installation team would remove the extending rod on the chosen carriers, add a spacer, and reinstall the extending rod.
Several problems have been noted with this procedure. First, access was difficult to the location of the connection between the extending rod and axis frame. The installers were forced to partially disassemble the tilt tray carrier in order to remove the extending rod. Second, once the spacers were installed, there was no visual indicator as to which carts were modified with the spacers. If a carrier were to need replacement, or if the bolt failed, there was no indicator that the particular cart had been effectively lengthened with a spacer.
Thus, there remains a need for a new and improved sorting conveyor in which the spacing between adjacent carts may be easily adjusted while, at the same time, the gap between adjacent carts may be monitored.
The present invention is directed to an improved sorting conveyor for transporting objects and unloading objects at one or more unloading stations adjacent the conveyor. Generally, the sorting conveyor includes: a conveyor track; a train of the tilting conveyor carts connected end-to-end; and a linear induction motor for moving the conveyor carts on the conveyor track.
Each of the tilting conveyor carts includes a trailer frame base. The trailer frame includes a roller structure for engaging the conveyor track, a driven member responsive to the linear induction motor including a guide roller assembly, and a hitch mechanism for connecting each tilting conveyor cart to an adjacent conveyor cart. The conveyor cart also includes a carrying tray for holding the objects and a tiltable support apparatus for supporting the carrying tray above the trailer frame base and for allowing tilting of the carrying tray towards at least one side of the conveyor to unload objects into unloading stations on at least one side of the conveyor.
The tilting mechanism tilts the carrying tray on the tiltable support apparatus to thereby unload objects into one of the unloading stations adjacent the conveyor. The improved tilting mechanism includes a pair of actuating arms attached to the carrying tray on opposite sides of the tiltable support apparatus and a pull-down mechanism associated with each unloading station for selectively pulling down one of the actuating arms so as to pull one side of the carrying tray downwardly into a tilted position.
In the present invention, each of the actuator arms includes a cam follower on a lower end of the actuator arm, and wherein the pull-down mechanism includes a descending ramp adjacent the conveyor track, and a laterally pivoting switch for directing the cam follower of a selected actuator arm into the descending ramp
The present invention modifies the connection to the leading cart with an adjustment spacer bar. The xe2x80x9cstandardxe2x80x9d connection bar is attached to the rearward end of the leading carrier. The standard connection bar is typically affixed to the carrier assembly by a pair of fasteners at opposing ends of the bar. A single hole is located in the standard connection bar. This hole receives a connecting bolt that connects the following cart through the following cart""s extending rod through a ball joint. This connecting hole was typically co-linear with the fastener holes, equally spaced between the fastener holes and located in the center of the standard connection bar.
The adjustment bar is designed to be affixed to the leading cart in place of the standard connection bar. The adjustment spacer bar differs in that the connection hole is not co-linear with the fastener holes. The preferred embodiment uses a {fraction (1/16)}th inch offset from the centerline of the adjustment spacer bar. Upon installation, if it is discovered that the train of carriers must be lengthened, the spacer bar is oriented in a way so that the offset hole is extending rearwardly from the centerline of the fastener holes. In this way, the effective length of the carrier is increased by {fraction (1/16)} inch.
Similarly, if the carriers must be shortened in order to fit on the track, the adjustment spacer bar is oriented in a way so that the offset hole is extending forwardly from the centerline of the fastener holes making the effective length of the carrier {fraction (1/16)}th inch shorter. The number of adjustment spacer bars will vary depending upon the length that must be increased or decreased to fit the carriers on the track. The adjustment spacer bars should preferably be located uniformly and evenly throughout the train of carts.
In order to allow immediate recognition of which carts have been effectively xe2x80x9clengthenedxe2x80x9d or xe2x80x9cshortened,xe2x80x9d the adjustment spacer bar can be colored differently from the normal spacer. In order to visually recognize whether the spacer was used to lengthen or shorten the effective length of the cart, the adjustment spacer bar can also be provided with some type of indicia, e.g., a chamfer on one comer, which would indicate whether the orientation was to lengthen or shorten.
Another significant aspect of the present invention is providing a gap monitor for monitoring gaps between successive carts. The gap monitor consists of three major elements: a plurality of detectable elements at predetermined positions on unique carts; at least one sensor for detecting the presence of the detectable elements; and, a comparator for evaluating the difference between the detectable elements and a reference value. The detectable elements can be the edges of unique carts and preferably are the trailing edge of a leading cart and the leading edge of the trailing cart. The sensor can be a proximity sensor and is preferably an inductive sensor. The comparator measures the difference in terms of time and the reference value is a predetermined distance.
In a preferred embodiment, the reference value is equal to the gap length between successive carts. If the gap monitor observes a value that is greater than the reference value, a signal will be sent to the controller and the sorter conveyor can be shut down for inspection of the gap.
Accordingly, one aspect of the present invention is to provide a sorting conveyor for transporting objects and unloading objects at one or more unloading stations adjacent the conveyor. The sorting conveyor includes: a conveyor track; a train of conveyor carts connected end-to-end; a power source for moving the conveyor carts on the conveyor track; each of the conveyor carts including: (i) a trailer frame base, including: a roller structure for engaging the conveyor track, a driven member responsive to the power source, and a hitch mechanism for connecting each conveyor cart to an adjacent conveyor cart; (ii) a carrying tray for holding the objects; and (iii) a tiltable support apparatus for supporting the carrying tray above the trailer frame base and for allowing tilting of the carrying tray towards at least one side of the conveyor to unload objects into unloading stations on at least one side of the conveyor; and an adjustment spacer between adjacent carts.
Another aspect of the present invention is to provide in a sorting conveyor for transporting objects and unloading objects at one or more unloading stations adjacent the conveyor, the sorting conveyor including: a conveyor track; a train of conveyor carts connected end-to-end; a power source for moving the conveyor carts on the conveyor track; each of the conveyor carts including: (i) a trailer frame base, including: a roller structure for engaging the conveyor track, a driven member responsive to the power source, and a hitch mechanism for connecting each conveyor cart to an adjacent conveyor cart; (ii) a carrying tray for holding the objects; and (iii) a tiltable support apparatus for supporting the carrying tray above the trailer frame base and for allowing tilting of the carrying tray towards at least one side of the conveyor to unload objects into unloading stations on at least one side of the conveyor, the improvement comprising an adjustment spacer between adjacent carts wherein the adjustment spacer is an adjustment spacer bar.
Still another aspect of the present invention is to provide a sorting conveyor for transporting objects and unloading objects at one or more unloading stations adjacent the conveyor. The sorting conveyor includes: a conveyor track; a train of conveyor carts connected end-to-end; a power source for moving the conveyor carts on the conveyor track; each of the conveyor carts including: (i) a trailer frame base, including: a roller structure for engaging the conveyor track, a driven member responsive to the power source, and a hitch mechanism for connecting each conveyor cart to an adjacent conveyor cart; (ii) a carrying tray for holding the objects; and (iii) a tiltable support apparatus for supporting the carrying tray above the trailer frame base and for allowing tilting of the carrying tray towards at least one side of the conveyor to unload objects into unloading stations on at least one side of the conveyor; an adjustment spacer between adjacent carts wherein the adjustment spacer is an adjustment spacer bar.; and a gap monitor for monitoring a gap between adjacent carts.